WO2016117968A1

WO2016117968A1 - Uplink mimo communication method in wireless communication system and apparatus therefor

Info

Publication number: WO2016117968A1
Application number: PCT/KR2016/000731
Authority: WO
Inventors: 김영태; 서한별; 채혁진; 김기준
Original assignee: 엘지전자 주식회사
Priority date: 2015-01-22
Filing date: 2016-01-22
Publication date: 2016-07-28
Also published as: US10243639B2; US20170373735A1

Abstract

Disclosed is a method for supporting uplink multiple-input and multiple-output (MIMO) in a wireless communication system. A method for transmitting data according to the present invention comprises the steps of: mapping, to first orthogonal frequency division multiplexing (OFDM) symbols within a subframe, first demodulation reference signals (DMRSs) corresponding to a first antenna port and a second DMRSs corresponding to a second antenna port; mapping, to second OFDM symbols except the first OFDM symbols within the subframe, first data corresponding to the first antenna port and second data corresponding to the second antenna port; and transmitting the subframe by using resources allocated to the uplink, wherein predetermined precodings are applied to the first data and the second data, and the predetermined precodings may be changed according to the index of the second OFDM symbols.

Description

Uplink MIMO communication method in wireless communication system and apparatus therefor

The present invention relates to a wireless communication system, and more particularly, to a method and apparatus for supporting wireless communication to which uplink multiple-input and multiple-output (MIMO) technology is applied.

Recently, with the spread of smartphones and tablet PCs and high-capacity multimedia communication, mobile traffic has been increasing rapidly. The increase in mobile traffic is expected to double about every year. Since most of this mobile traffic is transmitted through base stations, telecom service providers are faced with serious network load issues at the moment. As a result, service providers have increased network facilities to handle increasing traffic, and hastened to commercialize next-generation mobile communication standards that can efficiently handle large amounts of traffic such as mobile WiMAX and Long Term Evolution (LTE). But it's time for another solution to handle the ever-increasing volume of traffic.

In order to solve the above problems, D2D (Device to Device) communication has been studied. D2D communication is a distributed communication technology that directly passes traffic between adjacent nodes without using an infrastructure such as a base station. In a D2D communication environment, each node such as a portable terminal finds another physically adjacent terminal on its own, establishes a communication session, and transmits traffic. Since D2D communication can solve the traffic overload problem by distributing the concentrated traffic to the base station, it has been spotlighted as an element technology of the next generation mobile communication technology after 4G. For this reason, standards organizations such as the 3rd generation partnership project (3GPP) and the Institute of Electrical and Electronics Engineers (IEEE) are pursuing D2D communication standards based on LTE-Advanced (LTE-A) or Wi-Fi.

D2D communication is expected to not only contribute to improving the performance of mobile communication systems but also to create new communication services. It can also support services such as social network services or network games based on proximity. The D2D link can be used as a relay to solve the connectivity problem of the shadow area terminal. As such, D2D technology is expected to provide new services in various fields.

Meanwhile, communication technologies between devices such as infrared communication, ZigBee, radio frequency identification (RFID) and near field communications (NFC) based thereon have been widely used. However, these technologies only support special-purpose communications within a very limited distance (about 1m), so it is difficult to classify them as D2D communication technology that distributes the traffic of the base station.

On the other hand, since the terminal generally has a limited battery capacity, the transmitting terminal may transmit a signal with low power. Such low power signal transmission may degrade link reliability. Alternatively, multiple-input and multiple-output (MIMO) techniques can be applied to D2D communication. However, there is no specific proposal regarding a method of performing D2D communication using MIMO technology.

An object of the present invention is to provide a method and apparatus for applying a MIMO technology in uplink communication.

Another object of the present invention is to provide a method for allocating a demodulation reference signal for uplink MIMO.

Technical problems to be achieved in the present invention are not limited to the above technical problems, and other technical problems which are not mentioned will be clearly understood by those skilled in the art from the following description.

In one embodiment for achieving the above technical problem, a signal transmission method of a terminal on a wireless communication system supporting multiple antennas, the first antenna in the first Orthogonal Frequency Division Multiplexing (OFDM) symbols in a subframe (subframe) Mapping first demodulation reference signals (DMRSs) corresponding to the port and second DMRSs corresponding to the second antenna port; Mapping first data corresponding to the first antenna port and second data corresponding to the second antenna port to second OFDM symbols except for the first OFDM symbols in the subframe; And transmitting the subframe using a resource allocated to uplink, wherein predetermined precodings are applied to the first data and the second data, and the predetermined precoding is applied. They may be changed according to the index of the second OFDM symbols.

Preferably, the first data and the second data may be alternately mapped on the second OFDM symbols.

Preferably, the first data is mapped to be adjacent to an OFDM symbol to which the first DMRSs are mapped among the first OFDM symbols, and the second data is mapped to the second DMRSs of the first OFDM symbols. It may be mapped to be adjacent to an OFDM symbol.

Preferably, the predetermined precodings may be determined as one of predetermined precoding patterns.

Preferably, the method may further include transmitting information corresponding to the predetermined precoding to a receiving end.

Advantageously, said first OFDM symbols comprise four OFDM symbols, said first DMRSs are mapped onto two OFDM symbols of said first OFDM symbols, and said second DMRSs are said first OFDM symbols And may be mapped onto the remaining two OFDM symbols.

Preferably, one of the first OFDM symbols may be mapped to the first OFDM symbol of the subframe, and the rest of the first OFDM symbols may be mapped to each other at equal intervals on the time axis.

Advantageously, said first OFDM symbols have a length of half the length of said second OFDM symbol on a time axis, wherein each of said first DMRSs and each of said second DMRSs span two subcarriers. Can be mapped.

Advantageously, said first OFDM symbols comprise two OFDM symbols, wherein said first DMRS and said second DMRS are such that said first OFDM symbols share each of Resource Elements, and said first DMRS And the second DMRS may be separated using a cyclic shift and an orthogonal cover code.

Advantageously, the predetermined precodings may be changed according to the index of the second OFDM symbols and the subcarrier of the subframe.

Preferably, the predetermined precodings may be configured to have the same value every predetermined frequency period.

Preferably, the first DMRS and the second DMRS may be alternately mapped on resource elements of each of the first OFDM symbols.

In one embodiment for achieving the above technical problem, a signal reception method of a terminal on a wireless communication system supporting multiple antennas, the first antenna and the second of the transmitting end by using the resources allocated to the uplink (uplink) Receiving a subframe from an antenna; And estimating a channel from the first antenna and a channel from the second antenna based on predetermined precodings applied to first data from the first antenna and second data from the second antenna. And first demodulation reference signals (DMRSs) corresponding to the first antenna port to first orthogonal frequency division multiplexing (OFDM) symbols in the subframe. Corresponding second DMRSs are mapped, and first data corresponding to the first antenna port and second data corresponding to the second antenna port are included in second OFDM symbols except for the first OFDM symbols in the subframe. The predetermined precodings may be mapped and changed according to the indexes of the second OFDM symbols.

As one embodiment for achieving the above technical problem, a terminal on a wireless communication system that supports multiple antennas, the transmitter for transmitting a signal; And a processor configured to control the transmitter, wherein the processor includes: a first demodulation reference signal corresponding to a first antenna port in first orthogonal frequency division multiplexing (OFDM) symbols in a subframe; And first DMRSs corresponding to the first antenna port to second OFDM symbols excluding the first OFDM symbols in the subframe, and mapping second DMRSs corresponding to the second antenna port. And mapping second data corresponding to two antenna ports, and transmitting the subframe using resources allocated to uplink, and precoding preset to the first data and the second data. precodings are applied, and the preset precodings may be changed according to the indexes of the second OFDM symbols.

As one embodiment for achieving the above technical problem, a terminal on a wireless communication system supporting multiple antennas, the receiver for receiving a signal; And a processor configured to control the receiver, wherein the processor is configured to receive a subframe from a first antenna and a second antenna of a transmitting end by using a resource allocated to uplink. Further estimate the channel from the first antenna and the channel from the second antenna based on predetermined precodings applied to the first data from the first antenna and the second data from the second antenna. And first demodulation reference signals (DMRSs) corresponding to the first antenna port to first orthogonal frequency division multiplexing (OFDM) symbols in the subframe, and a second corresponding to the second antenna port. DMRSs are mapped, first data corresponding to the first antenna port to second OFDM symbols excluding the first OFDM symbols in the subframe, and Group and the second data is mapped corresponding to the second antenna port, the predetermined pre-coding may be used only as an index of the second OFDM symbol.

According to embodiments of the present invention, diversity may be obtained by applying MIMO to uplink.

In addition, according to embodiments of the present invention, demodulation reference signals for a plurality of channels may be transmitted while maintaining resources for uplink data transmission.

In addition, according to embodiments of the present invention, the reception performance at the receiving end may be improved.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide examples of the present invention and together with the description, describe the technical idea of the present invention.

1 is a block diagram showing the configuration of a base station and a terminal in a wireless communication system.

2A and 2B illustrate the structure of a downlink radio frame.

3 is a diagram illustrating a resource grid in a downlink slot.

4 is a diagram illustrating a structure of a downlink subframe.

5 is a diagram illustrating a structure of an uplink subframe.

6A and 6B are schematic diagrams of a general MIMO communication system.

FIG. 7 illustrates a structure of a downlink reference signal for a normal CP in an LTE system supporting downlink transmission using four antennas.

FIG. 8 is a diagram illustrating a structure of a downlink reference signal for an extended CP in an LTE system supporting downlink transmission using four antennas.

9 is an example of a periodic CSI-RS transmission scheme.

10 is an example of an aperiodic CSI-RS transmission scheme.

11 shows a simplified D2D communication network.

12 illustrates a configuration of a resource unit according to an example.

13 illustrates a periodic Scheduling Assignment (SA) resource pool according to an example.

14A and 14B show an example of allocation of the DMRS according to the first embodiment.

15A and 15B show an example of antenna port allocation according to the first embodiment.

16A and 16B show another example of antenna port allocation according to the first embodiment.

17A and 17B show an example of DMRS allocation according to the second embodiment.

18A and 18B show an example of antenna port allocation according to the second embodiment.

19A and 19B show another example of antenna port allocation according to the second embodiment.

20A and 20B show another example of DMRS allocation according to the second embodiment.

21A and 21B show another example of DMRS allocation according to the second embodiment.

22A and 22B show an example of DMRS allocation according to the third embodiment.

23A and 23B show an example of DMRS allocation according to the fourth embodiment.

24A and 24B show another example of DMRS allocation according to the fourth embodiment.

25A and 25B show an example of DMRS allocation according to the fifth embodiment.

26A and 26B show an example of DMRS allocation for four antenna ports according to the fifth embodiment.

27A and 27B show another example of DMRS allocation for four antenna ports according to the fifth embodiment.

28A and 28B show another example of DMRS allocation for four antenna ports according to the fifth embodiment.

The following embodiments combine the components and features of the present invention in a predetermined form. Each component or feature may be considered to be optional unless otherwise stated. Each component or feature may be embodied in a form that is not combined with other components or features. In addition, some components and / or features may be combined to form an embodiment of the present invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment.

In this specification, a base station has a meaning as a network terminal node that directly communicates with a terminal. Certain operations described herein as being performed by a base station may in some cases be performed by an upper node of the base station. That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station.

In this specification, the term 'base station (BS)' may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), and an access point (AP). The repeater may be replaced by terms such as relay node (RN) and relay station (RS). In addition, the term “terminal” may be replaced with terms such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), and a subscriber station (SS).

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802 system, 3GPP system, 3GPP LTE and LTE-Advanced (LTE-A) system and 3GPP2 system. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

Further, embodiments of the present invention include Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and Single Carrier Frequency Division Multiple (SC-FDMA). It can be used in various wireless access systems such as Access). CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, E-Utra (Evolved UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (Advanced) is the evolution of 3GPP LTE. WiMAX can be described by the IEEE 802.16e standard (WirelessMAN-OFDMA Reference System) and the advanced IEEE 802.16m standard (WirelessMAN-OFDMA Advanced system). For clarity, the following description focuses on 3GPP LTE and 3GPP LTE-A systems, but the technical spirit of the present invention is not limited thereto.

In addition, specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

1 is a block diagram showing the configuration of a base station 105 and a terminal 110 in a wireless communication system 100.

Although one base station 105 and one terminal 110 (including a D2D terminal) are shown to simplify the wireless communication system 100, the wireless communication system 100 may include one or more base stations and / or one or more base stations. It may include a terminal.

Referring to FIG. 1, the base station 105 includes a transmit (Tx) data processor 115, a symbol modulator 120, a transmitter 125, a transmit / receive antenna 130, a processor 180, a memory 185, and a receiver ( 190, a symbol demodulator 195, and a receive data processor 197. The terminal 110 transmits (Tx) the data processor 165, the symbol modulator 170, the transmitter 175, the transmit / receive antenna 135, the processor 155, the memory 160, the receiver 140, and the symbol. It may include a demodulator 155 and a receive data processor 150. Although the transmit and receive

antennas

130 and 135 are shown as one in the base station 105 and the terminal 110, respectively, the base station 105 and the terminal 110 are provided with a plurality of transmit and receive antennas. Accordingly, the base station 105 and the terminal 110 according to the present invention support a multiple input multiple output (MIMO) system. In addition, the base station 105 according to the present invention may support both a single user-MIMO (SU-MIMO) and a multi-user-MIMO (MU-MIMO) scheme.

On the downlink, the transmit data processor 115 receives the traffic data, formats the received traffic data, codes it, interleaves and modulates (or symbol maps) the coded traffic data, and modulates the symbols ("data"). Symbols "). The symbol modulator 120 receives and processes these data symbols and pilot symbols to provide a stream of symbols.

The symbol modulator 120 multiplexes the data and pilot symbols and sends them to the transmitter 125. In this case, each transmission symbol may be a data symbol, a pilot symbol, or a signal value of zero. In each symbol period, pilot symbols may be sent continuously. The pilot symbols may be frequency division multiplexed (FDM), orthogonal frequency division multiplexed (OFDM), time division multiplexed (TDM), or code division multiplexed (CDM) symbols.

Transmitter 125 receives the stream of symbols and converts it into one or more analog signals, and further adjusts (eg, amplifies, filters, and frequency upconverts) the analog signals to provide a wireless channel. Generates a downlink signal suitable for transmission via the transmission antenna 130, the transmission antenna 130 transmits the generated downlink signal to the terminal.

In the configuration of the terminal 110, the receiving antenna 135 receives the downlink signal from the base station and provides the received signal to the receiver 140. Receiver 140 adjusts the received signal (eg, filtering, amplifying, and frequency downconverting), and digitizes the adjusted signal to obtain samples. The symbol demodulator 145 demodulates the received pilot symbols and provides them to the processor 155 for channel estimation.

The symbol demodulator 145 also receives a frequency response estimate for the downlink from the processor 155 and performs data demodulation on the received data symbols to obtain a data symbol estimate (which is an estimate of the transmitted data symbols). Obtain and provide data symbol estimates to a receive (Rx) data processor 150. Receive data processor 150 demodulates (ie, symbol de-maps), deinterleaves, and decodes the data symbol estimates to recover the transmitted traffic data.

The processing by symbol demodulator 145 and receiving data processor 150 is complementary to the processing by symbol modulator 120 and transmitting data processor 115 at base station 105, respectively.

The terminal 110 is on the uplink, and the transmit data processor 165 processes the traffic data to provide data symbols. The symbol modulator 170 may receive and multiplex data symbols, perform modulation, and provide a stream of symbols to the transmitter 175. The transmitter 175 receives and processes a stream of symbols to generate an uplink signal. The transmit antenna 135 transmits the generated uplink signal to the base station 105.

In the base station 105, an uplink signal is received from the terminal 110 through the reception antenna 130, and the receiver 190 processes the received uplink signal to obtain samples. The symbol demodulator 195 then processes these samples to provide received pilot symbols and data symbol estimates for the uplink. The received data processor 197 processes the data symbol estimates to recover the traffic data transmitted from the terminal 110.

Processors

155 and 180 of the terminal 110 and the base station 105 respectively instruct (eg, control, coordinate, manage, etc.) operations at the terminal 110 and the base station 105, respectively.

Respective processors

155 and 180 may be connected to memory units 160 and 185 that store program codes and data. The memory 160, 185 is coupled to the processor 180 to store the operating system, applications, and general files.

The

processors

155 and 180 may also be referred to as controllers, microcontrollers, microprocessors, microcomputers, or the like. The

processors

155 and 180 may be implemented by hardware or firmware, software, or a combination thereof. When implementing embodiments of the present invention using hardware, application specific integrated circuits (ASICs) or digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) configured to perform the present invention. Field programmable gate arrays (FPGAs) may be provided in the

processors

155 and 180.

Meanwhile, when implementing embodiments of the present invention using firmware or software, the firmware or software may be configured to include a module, a procedure, or a function for performing the functions or operations of the present invention, and to perform the present invention. The firmware or software configured to be may be provided in the

processors

155 and 180 or stored in the memory 160 and 185 to be driven by the

processors

155 and 180.

The layers of the air interface protocol between the terminal and the base station between the wireless communication system (network) are based on the lower three layers of the open system interconnection (OSI) model, which is well known in the communication system. ), And the third layer L3. The physical layer belongs to the first layer and provides an information transmission service through a physical channel. A Radio Resource Control (RRC) layer belongs to the third layer and provides control radio resources between the UE and the network. The terminal and the base station may exchange RRC messages through the wireless communication network and the RRC layer.

In the present specification, the processor 155 of the terminal and the processor 180 of the base station perform operations of processing signals and data except for a function of receiving or transmitting a signal and a storage function of the terminal 110 and the base station 105, respectively. In the following description, the

processor

155 and 180 are not specifically mentioned. Although not specifically mentioned by the

processors

155 and 180, it may be said that a series of operations such as a function of receiving or transmitting a signal and a data processing other than a storage function are performed.

LTE / LTE-A Resource Structure / Channel

A structure of a downlink radio frame will be described with reference to FIGS. 2A and 2B.

In a cellular OFDM wireless packet communication system, uplink / downlink data packet transmission is performed in subframe units, and one subframe is defined as a predetermined time interval including a plurality of OFDM symbols. The 3GPP LTE standard supports a type 1 radio frame structure applicable to frequency division duplex (FDD) and a type 2 radio frame structure applicable to time division duplex (TDD). In particular, FIG. 2A illustrates a frame structure for frequency division duplex (FDD) used in 3GPP LTE / LTE-A system, and FIG. 2B illustrates a frame structure for time division duplex (TDD) used in 3GPP LTE / LTE-A system. It is shown.

2A illustrates a structure of a type 1 radio frame. A radio frame has a length of 10 ms (327200 x T _s ) and consists of 10 equally sized subframes. Each subframe has a length of 1 ms and consists of two slots. Each slot has a length of 0.5 ms (15360 x T _s ). Here, T _s represents a sampling time and is represented by T _s = 1 / (15 kHz x 2048) = 3.2552 x 10 ^-8 (about 33 ns). The slot includes a plurality of OFDM symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. In an LTE system, one resource block includes 12 subcarriers x 7 (or 6) OFDM symbols. 20 slots in one radio frame may be sequentially numbered from 0 to 19. Each slot is 0.5ms long. The time for transmitting one subframe is defined as a transmission time interval (TTI). The time resource may be classified by a radio frame number (also called a radio frame index), a subframe number (also called a subframe number), a slot number (or slot index), and the like.

2B is a diagram illustrating a structure of a type 2 radio frame. Type 2 radio frames consist of two half frames, each of which has five subframes, a downlink pilot time slot (DwPTS), a guard period (GP), and an uplink pilot time slot (UpPTS). One subframe consists of two slots. DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. The guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink. On the other hand, one subframe consists of two slots regardless of the radio frame type.

The radio frame may be configured differently according to the duplex mode. For example, in the frequency division duplex (FDD) mode, since downlink transmission and uplink transmission are divided by frequency, a radio frame includes only one of a downlink subframe or an uplink subframe for a specific frequency band. In the TDD mode, since downlink transmission and uplink transmission are separated by time, a radio frame includes both a downlink subframe and an uplink subframe for a specific frequency band.

Table 1 illustrates a DL-UL configuration of subframes in a radio frame in the TDD mode.

Table 1

DL-UL configuration

Downlink-to-Uplink Switch-point periodicity

Subframe number

0

One

2

3

4

5

6

7

8

9

0

5 ms

D

S

U

D

S

U

One

5 ms

D

S

U

D

S

U

D

2

5 ms

D

S

U

D

S

U

D

3

10 ms

D

S

U

D

4

10 ms

D

S

U

D

5

10 ms

D

S

U

D

6

5 ms

D

S

U

D

S

U

D

In Table 1, D represents a downlink subframe, U represents an uplink subframe, and S represents a special subframe. The singular subframe includes three fields of Downlink Pilot TimeSlot (DwPTS), Guard Period (GP), and Uplink Pilot TimeSlot (UpPTS). DwPTS is a time interval reserved for downlink transmission, and UpPTS is a time interval reserved for uplink transmission. Table 2 illustrates the configuration of a singular frame.

TABLE 2

Special subframe configuration	Normal cyclic prefix in downlink			Extended cyclic prefix in downlink
	DwPTS	UpPTS		DwPTS	UpPTS
		Normal cyclic prefix in uplink	Extended cyclic prefix in uplink		Normal cyclic prefix in uplink	Extended cyclic prefix in uplink
0	6592T _s	2192T _s	2560T _s	7680T _s	2192T _s	2560T _s
One	19760T _s			20480T _s
2	21952T _s			23040T _s
3	24144T _s			25600T _s
4	26336T _s			7680T _s	4384T _s	5120T _s
5	6592T _s	4384T _s	5120T _s	20480T _s
6	19760T _s			23040T _s
7	21952T _s			-	-	-
8	24144T _s			-	-	-

The structure of the radio frame described above is merely an example, and the number of subframes included in the radio frame, the number of slots included in the subframe, and the number of symbols included in the slot may be variously changed.

3 is a diagram illustrating a resource grid in a downlink slot. One downlink slot includes seven OFDM symbols in the time domain, and one resource block (RB) is shown to include twelve subcarriers in the frequency domain, but the present invention is not limited thereto. For example, one slot includes seven OFDM symbols in the case of a general cyclic prefix (CP), but one slot may include six OFDM symbols in the case of an extended-CP (CP). Each element on the resource grid is called a resource element. One resource block includes 12x7 resource elements. The number of N ^DLs of resource blocks included in the downlink slot depends on the downlink transmission bandwidth. The structure of the uplink slot may be the same as the structure of the downlink slot.

4 is a diagram illustrating a structure of a downlink subframe. Up to three OFDM symbols in front of the first slot in one subframe correspond to a control region to which a control channel is allocated. The remaining OFDM symbols correspond to data regions to which a physical downlink shared channel (PDSCH) is allocated. The downlink control channels used in the 3GPP LTE system include, for example, a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), and a physical HARQ indicator channel. (PHICH: Physical Hybrid automatic repeat request Indicator CHannel). The PCFICH is transmitted in the first OFDM symbol of a subframe and includes information on the number of OFDM symbols used for control channel transmission in the subframe. The PHICH includes a HARQ Acknowledgment (ACK) / NACK (Negative ACK) signal as a response to uplink transmission. Control information transmitted through the PDCCH is referred to as downlink control information (DCI). DCI includes uplink or downlink scheduling information or an uplink transmit power control command for a certain terminal group. The PDCCH includes a resource allocation and transmission format of a DL shared channel (DL-SCH), resource allocation information of an uplink shared channel (UL-SCH), paging information of a paging channel (PCH), system information on a DL-SCH, and PD- Resource allocation of upper layer control messages, such as random access responses transmitted on the SCH, sets of transmit power control commands for individual terminals in any terminal group, transmit power control information, Voice over IP (VoIP) Activation may be included. A plurality of PDCCHs may be transmitted in the control region. The terminal may monitor the plurality of PDCCHs. The PDCCH is transmitted in an aggregation of one or more consecutive control channel elements (CCEs). CCE is a logical allocation unit used to provide a PDCCH with a coding rate based on the state of a radio channel. The CCE corresponds to a plurality of resource element groups. The PDCCH format and the number of available bits are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs. The base station determines the PDCCH format according to the DCI transmitted to the terminal, and adds a cyclic redundancy check (CRC) to the control information. The CRC is masked with an identifier called Radio Network Temporary Identifier (RNTI) according to the owner or purpose of the PDCCH. If the PDCCH is for a specific terminal, the cell-RNTI (C-RNTI) identifier of the terminal may be masked to the CRC. Or, if the PDCCH is for a paging message, a paging indicator identifier, eg, Paging-RNTI (P-RNTI), may be masked in the CRC. If the PDCCH is for system information (more specifically, System Information Block (SIB)), the system information identifier and system information RNTI (SI-RNTI) may be masked to the CRC. Random Access-RNTI (RA-RNTI) may be masked to the CRC to indicate a random access response that is a response to transmission of a random access preamble of the terminal.

5 is a diagram illustrating a structure of an uplink subframe. The uplink subframe may be divided into a control region and a data region in the frequency domain. A physical uplink control channel (PUCCH) including uplink control information is allocated to the control region. A physical uplink shared channel (PUSCH) including user data is allocated to the data area. In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH. PUCCH for one UE is allocated to an RB pair in a subframe. Resource blocks belonging to a resource block pair occupy different subcarriers for two slots. This is called a resource block pair allocated to the PUCCH is frequency-hopped at the slot boundary.

Multi-antenna system

Multiple-Input and Multiple-Output (MIMO) technology is an application of a technique of gathering and completing fragmented pieces of data received from multiple antennas without relying on a single antenna path to receive a message. Multi-antenna technology is a next-generation mobile communication technology that can be widely used in mobile communication terminals and repeaters because it can improve the data transmission speed in a specific range or increase the system range for a specific data transmission speed. It is attracting attention as the next generation technology that can overcome the traffic limit of mobile communication which reached the limit situation.

6A is a configuration diagram of a general multiple antenna (MIMO) communication system. As shown in FIG. 6A, when the number of transmitting antennas is increased to N _{T and the} number of receiving antennas is increased to N _R at the same time, unlike the case where a plurality of antennas are used only in a transmitter or a receiver, the number of channels is theoretically proportional to the number of antennas. The transmission capacity is increased. Therefore, it is possible to improve transmission rate and significantly improve frequency efficiency. The transmission rate according to the increase in the channel transmission capacity may theoretically increase as the maximum rate R0 in the case of using one antenna is multiplied by the increase rate R _i of Equation 1 below.

[Equation 1]

For example, in a MIMO communication system using four transmit antennas and four receive antennas, a theoretical transmission rate of four times can be obtained for a single antenna system. Since the theoretical capacity increase of the multi-antenna system was proved in the mid-90s, various technologies have been actively studied to lead to substantial data rate improvement. Some of these technologies have already been developed for 3G mobile communication and next generation WLAN. Is reflected in the various standards of wireless communication.

The research trends related to multi-antennas to date include information theory aspects related to calculation of multi-antenna communication capacity in various channel environments and multi-access environments, wireless channel measurement and model derivation of multi-antenna systems, and transmission reliability and transmission rate improvement. Active research is being conducted from various viewpoints, such as the study of space-time signal processing technology.

In order to describe the communication method in the multi-antenna system in a more specific manner, it can be represented as follows mathematically. Assume that there are N _T transmit antennas and N _R receive antennas as shown in FIG. 6A. First, referring to the transmission signal, when there are N _T transmit antennas, since the maximum transmittable information is N _T , the transmission information may be represented by a vector shown in Equation 2 below.

[Equation 2]

Meanwhile, each transmission information

Can have different transmit powers.

In this case, the transmission information of which transmission power is adjusted is represented by a vector as shown in Equation 3 below.

[Equation 3]

Also,

Is expressed using the diagonal matrix P of the transmission power, as shown in Equation 4 below.

[Equation 4]

On the other hand, information vector with adjusted transmission power

N _T transmitted signals that are actually transmitted by applying the weight matrix W to

Consider the case where is configured. Here, the weight matrix plays a role of properly distributing transmission information to each antenna according to a transmission channel situation. Such a transmission signal

Can be expressed as Equation 5 below using the vector x. here

Denotes a weight between the i th transmission antenna and the j th information. W is called a weight matrix or a precoding matrix.

[Equation 5]

Receive signal of each antenna when there are N _R receiving antennas

When expressed as a vector is as shown in Equation 6 below.

[Equation 6]

Meanwhile, when modeling a channel in a multi-antenna communication system, channels may be classified according to transmit / receive antenna indexes, and a channel passing through the receive antenna i from the transmit antenna j will be denoted as h _ij . Here, it is noted that the order of the index of h _ij is that the reception antenna index is first, and the index of the transmission antenna is later.

These channels can be grouped together and displayed in vector and matrix form. An example of the vector display is described as follows. 6B illustrates a channel from N _T transmit antennas to receive antenna i.

As shown in FIG. 6B, a channel arriving from the N _T transmit antennas to the reception antenna i may be expressed as follows.

[Equation 7]

In addition, when all the channels passing from the N _T transmit antennas to the N _R receive antennas are expressed through the matrix representation as shown in Equation 7, Equation 8 below.

[Equation 8]

The real channel is added with Additive White Gaussian Noise (AWGN) after passing through the channel matrix H as described above, so that the white noise added to each of the N _R receiving antennas

When expressed as a vector is expressed by the following equation (9).

[Equation 9]

The received signal obtained using the above equations is shown in Equation 10 below.

[Equation 10]

On the other hand, the number of rows and columns of the channel matrix H representing the channel condition is determined by the number of transmit antennas and receive antennas. The number of rows in the channel matrix H is equal to the number of receive antennas N _R , and the number of columns is equal to the number of transmit antennas N _T. That is, the channel matrix H may be represented by an N _R × N _T matrix. In general, the rank of a matrix is defined by the smaller of the number of rows and columns independent of each other. Therefore, the rank of the matrix cannot have a value larger than the number of rows or columns of the matrix. The rank of the channel matrix H can be represented by the following equation (11).

[Equation 11]

Multiple antenna transmit / receive schemes used for the operation of multiple antenna systems include frequency switched transmit diversity (FST), Space Frequency Block Code (SFBC), Space Time Block Code (STBC), and Cyclic Delay Diversity (CDD). TSTD (time switched transmit diversity) may be used. In Rank 2 or higher, spatial multiplexing (SM), Generalized Cyclic Delay Diversity (GCDD), Selective Virtual Antenna Permutation (S-VAP), and the like may be used.

FSTD is a method of obtaining diversity gain by allocating subcarriers having different frequencies for each signal transmitted to each of the multiple antennas. SFBC is a technique that efficiently applies selectivity in the spatial domain and frequency domain to secure both diversity gain and multi-user scheduling gain in the corresponding dimension. STBC is a technique for applying selectivity in the space domain and the time domain. CDD is a technique of obtaining diversity gain by using path delay between transmission antennas. TSTD is a technique of time-dividing a signal transmitted through multiple antennas. Spatial multiplexing is a technique to increase the data rate by transmitting different data for each antenna. GCDD is a technique for applying selectivity in the time domain and the frequency domain. S-VAP is a technique using a single precoding matrix. Multi-codeword (MCW) S, which mixes multiple codewords between antennas in spatial diversity or spatial multiplexing, and Single Codeword (SCW) S using single codeword. There is a VAP.

Reference Signal Received Power (RSRP)

RSRP is defined as the linear average of the power of the resource elements carrying a cell-specific RS (CRS) within the measured frequency bandwidth. The UE may determine an RSRP by detecting a cell-specific reference signal (CRS) mapped and transmitted on a specific resource element. In the RSRP calculation, the cell-specific reference signal R0 for antenna port 0 can be used basically. If R-cell can detect the cell-specific reference signal R1 for antenna port 1 reliably, R1 is added to R0. Can be used to determine RSRP. For detailed information on the cell-specific reference signal, reference may be made to a standard document (eg, 3GPP TS36.211).

LTE Received Signal Strength Indicator (RSSI)

RSSI may be defined as the total received wideband power from all sources, including co-channel serving and non-serving cells, adjacent channel interference, thermal noise, etc. within the measurement band observed by the terminal. RSSI may be used as an input for Reference Signal Received Quality (RSRQ), which will be described later.

Reference Signal Received Quality (RSRQ)

RSRQ is intended to provide cell-specific signal quality characteristics and is similar to RSRP, but RSRQ may be mainly used for ranking different LTE candidate cells according to signal quality of each cell. For example, where RSRP measurements provide insufficient information to make stable mobility decisions, RSRQ measurements may be used as input for handover and cell reselection decisions. A value obtained by multiplying the number N of resource blocks within a frequency bandwidth to be divided by LTE carrier RSSI (ie, RSRQ = N × RSRP / (E-UTRA carrier RSSI)). The numerator (N × RSRP) and denominator (E-UTRA carrier RSSI) are measured for the same set of resource blocks. While RSRP is an indicator of the desired signal strength, RSRQ may allow for an effective way to report the combined effects of signal strength and interference by taking into account the level of interference included in the RSSI.

Reference Signal (RS)

In a mobile communication system, since a packet is transmitted through a wireless channel, signal distortion may occur. In addition, the receiver must know the channel information in order to correct the distorted signal on the receiver side. Therefore, in order to find out the channel information, the transmitting side transmits a signal known to both the transmitting side and the receiving side, and the receiving side mainly uses a method of finding the channel information according to the degree of distortion of the received signal. In this case, a signal known to both the transmitting side and the receiving side is called a pilot signal or a reference signal (RS). In addition, in wireless communication in which multiple antenna (MIMO) technology is applied, a separate reference signal exists for each transmit antenna.

In a mobile communication system, a reference signal may be classified into a reference signal for obtaining channel information and a reference signal for data demodulation. Since a reference signal for channel information acquisition is intended for a terminal to acquire channel information in downlink, the terminal is transmitted over a wide band and a terminal that does not receive downlink data in a specific subframe may receive and measure the reference signal. It should be possible. In addition, the reference signal for channel information acquisition may also be used for channel state measurement for handover. The reference signal for data demodulation is a reference signal transmitted together with a downlink resource when the base station transmits downlink data. The terminal may perform channel estimation and demodulate data by receiving the reference signal. The reference signal for demodulation is transmitted in the area where data is transmitted.

In the LTE system, two types of downlink reference signals are defined for unicast services. Common RS and CRS for acquiring information on channel status and measuring the handover, and UE-specific RS used for data demodulation. In the LTE system, the UE-specific reference signal is used only for data demodulation and the CRS may be used for both channel information acquisition and data demodulation. The CRS is a cell-specific signal and may be transmitted every subframe in the case of wideband.

In LTE-A (LTE-Advanced), a reference signal capable of supporting up to eight transmit antennas is required. In order to support 8 transmit antennas while maintaining backward-compatibility with the LTE system, an additional 8 transmit antennas in the time-frequency domain in which the CRS defined in LTE is transmitted every subframe in all bands The reference signal needs to be defined. However, in the LTE-A system, when a reference signal for up to eight antennas is added in the same manner as the CRS of the conventional LTE, the overhead due to the reference signal is excessively increased. Accordingly, in LTE-A, as a reference signal for channel measurement purpose for selecting a modulation and coding scheme (MCS), a precoding matrix indicator (PMI), and the like, a channel state information reference signal (CSI-RS) And a decoding-reference signal (DM-RS) for data demodulation. Unlike conventional CRSs used for data demodulation at the same time as channel measurement, handover, etc., CSI-RS is transmitted only for the purpose of obtaining information on channel status. Therefore, the CSI-RS may not be transmitted every subframe. In order to reduce the overhead due to the CSI-RS, the CSI-RS is intermittently transmitted in the time domain, and the DM-RS for the corresponding UE is transmitted for data demodulation. Accordingly, the DM-RS of a specific terminal is transmitted only in a region where the terminal is scheduled, that is, in a time-frequency region in which the specific terminal receives data.

7 and 8 illustrate a structure of a reference signal in an LTE system supporting downlink transmission using four antennas. In particular, FIG. 7 illustrates a case of normal cyclic prefix, and FIG. 8 illustrates a case of extended cyclic prefix.

Referring to FIGS. 7 and 8, 0 to 3 described in the lattice mean a common reference signal (CRS), which is a cell-specific reference signal transmitted for channel measurement and data demodulation corresponding to each of antenna ports 0 to 3. The CRS, which is a cell specific reference signal, may be transmitted to the terminal not only in the data information region but also in the control information region.

In addition, 'D' described in the grid means downlink DM-RS (DM-RS), which is a UE-specific RS, and the DM-RS supports single antenna port transmission through a data region, that is, a PDSCH. The terminal is signaled through the upper layer whether the DM-RS which is the terminal specific RS is present. 7 and 8 illustrate DM-RSs corresponding to antenna port 5, and 3GPP standard document 36.211 also defines DM-RSs for antenna ports 7 to 14, that is, a total of eight antenna ports.

For example, the reference signal mapping rule to the resource block may be according to the following equations.

In the case of CRS, a reference signal may be mapped according to Equation 12 below.

[Equation 12]

In addition, in the dedicated RS, a reference signal may be mapped according to Equation 13 below.

[Equation 13]

In

Equations

12 and 13, k denotes an antenna port having a subcarrier index p. In addition, N _DL ^RB denotes the number of resource convex allocated to downlink, n _s denotes a slot index, and N _ID ^cell denotes a cell ID.

In the LTE-A system, the base station transmits CSI-RS for all antenna ports. As described above, the CSI-RS may be transmitted intermittently in the time domain. For example, the CSI-RS may be transmitted periodically with an integer multiple of one subframe or may be transmitted in a specific transmission pattern. In this case, the period / pattern in which the CSI-RS is transmitted may be set by the base station. In order to measure a channel using the CSI-RS, the UE transmits the CSI-RS transmission subframe index for the CSI-RS antenna port of the cell to which the cell belongs, the CSI-RS resource element time-frequency position in the transmission subframe, and the CSI-RS. You need to know information such as RS sequence.

In the LTE-A system, resources used for CSI-RS transmission of different antenna ports are orthogonal to each other. When a base station transmits CSI-RSs for different antenna ports, it maps the CSI-RSs for each antenna port to different resource elements, thereby making them available in a frequency division multiplexing (FDM) / time division multiplexing (TDM) scheme. Resources can be allocated to be orthogonal to one another. In addition, the base station may transmit the CSI-RS in a code division multiplexing scheme by mapping CSI-RSs for different antenna ports using codes orthogonal to each other.

9 is an example of a periodic CSI-RS transmission scheme. In FIG. 9, the CSI-RS is transmitted at a period of 10 ms, and the offset is three. The offset value may have a different value for each base station so that the CSI-RSs of the various cells may be evenly distributed to each other. When the CSI-RS is transmitted in a period of 10 ms, the offset that the base station may have is 10 values of 0 to 9. The offset indicates an index value of a subframe in which a base station having a specific period starts CSI-RS transmission. When the base station informs the period and the offset value of the CSI-RS, the terminal measures the CSI-RS of the base station at the corresponding location using the corresponding value and reports information such as CQI / PMI / RI to the base station. All information related to the CSI-RS is cell-specific information.

10 is an illustration of an aperiodic CSI-RS transmission scheme. In FIG. 10, the base station transmits CSI-RSs at

subframe indexes

3 and 4. The transmission pattern is composed of 10 subframes, and whether or not to transmit CSI-RS in each subframe may be designated by a bit indicator.

In general, two methods are considered as a method in which the base station informs the UE of the CSI-RS configuration.

First, the base station may transmit the CSI-RS configuration using DBCH signaling (Dynamic Broadcast CHannel) in which the base station broadcasts the CSI-RS configuration information to the terminals. In the LTE system, BCH (Broadcasting CHannel) is used to inform the UE of system information. However, when the amount of information is large and cannot be transmitted by the BCH, the information is transmitted in the same manner as general data, and the SI-RNTI (System Information RNTI) is transmitted by CR-masking the PDCCH of the data rather than the specific terminal ID. . In this case, the actual system information is transmitted in the PDSCH region like general unicast data. All UEs in a cell can obtain system information by decoding the PDCCH using SI-RNTI and decoding the PDSCH indicated by the corresponding PDCCH. Such a broadcasting method may be referred to as a DBCH, distinguished from a physical BCH (PBCH), which is a general broadcasting method. The system information broadcast in the LTE system is a MIB (Master Information Block) transmitted to the PBCH and a SIB (System Information Block) transmitted multiplexed with general unicast data in the PDSCH. SIB9 newly introduced in LTE-A. The CSI-RS configuration may be transmitted using SIB10 or the like.

In addition, the base station may transmit the CSI-RS-related information to the terminal using Radio Resource Control (RRC) signaling. In the process of establishing a connection with the base station through initial access or handover, the base station may transmit CSI-RS configuration to the terminal using RRC signaling. In addition, the base station may transmit the CSI-RS configuration information to the terminal through an RRC signaling message requesting feedback based on the CSI-RS measurement.

Hereinafter, various embodiments in which a terminal performs device to device communication (hereinafter, may be referred to as D2D communication or D2D direct communication) will be described. Although 3GPP LTE / LTE-A is described as an example for description, D2D communication may be applied to and used in other communication systems (IEEE 802.16, WiMAX, etc.).

D2D communication type

The D2D communication may be classified into a network coordinated D2D communication type and an autonomous D2D communication type according to whether D2D communication is performed through control of a network. The network cooperative D2D communication type may be further classified into a type in which only D2D transmits data (data only in D2D) and a type in which a network performs connection control only (Connection control only in network) according to the degree of network involvement. For convenience of explanation, hereinafter, a type in which only D2D transmits data will be referred to as a 'network-intensive D2D communication type', and a type in which a network performs only connection control will be referred to as a 'distributed D2D communication type'.

In the network centralized D2D communication type, only data is exchanged between D2D terminals, and connection control and radio resource allocation between the D2D terminals are performed by a network. D2D terminals may transmit and receive data or specific control information by using a radio resource allocated by a network. For example, HARQ ACK / NACK feedback or channel state information (CSI) for data reception between D2D terminals may be transmitted to other D2D terminals through a network rather than directly exchanged between the D2D terminals. Specifically, if the network establishes a D2D link between the D2D terminals and allocates a radio resource to the established D2D link, the transmitting D2D terminal and the receiving D2D terminal may perform D2D communication using the allocated radio resource. That is, in the network centralized D2D communication type, D2D communication between D2D terminals is controlled by a network, and the D2D terminals may perform D2D communication using radio resources allocated by the network.

The network in the distributed D2D communication type plays a more limited role than the network in the network centralized D2D communication type. In the distributed D2D communication type, the network performs access control between the D2D terminals, but the radio resource allocation (grant message) between the D2D terminals may be occupied by the D2D terminals by themselves without competition. For example, HARQ ACK / NACK feedback or channel state information for data reception between D2D terminals for data reception between D2D terminals may be directly exchanged between D2D terminals without passing through a network.

As in the above-described example, D2D communication may be classified into a network-intensive D2D communication type and a distributed D2D communication type according to the degree of D2D communication intervention of the network. At this time, a common feature of the network-centralized D2D communication type and the distributed D2D communication type is that D2D access control can be performed by a network.

Specifically, a network in a network cooperative D2D communication type may establish a connection between D2D terminals by establishing a D2D link between D2D terminals to perform D2D communication. In setting the D2D link between the D2D terminals, the network may assign a physical D2D link identifier (LID) to the configured D2D link. The physical D2D link ID may be used as an identifier for identifying each of a plurality of D2D links between the plurality of D2D terminals.

In the autonomous D2D communication type, unlike the network centralized and distributed D2D communication types, D2D terminals can freely perform D2D communication without the help of a network. That is, in the autonomous D2D communication type, the D2D UE performs access control and occupation of radio resources by itself, unlike in the network-intensive and distributed D2D communication. If necessary, the network may provide the D2D user equipment with D2D channel information that can be used in the corresponding cell.

Setting up a D2D communication link

For convenience of description herein, a terminal capable of performing or performing D2D communication, which is direct communication between terminals, will be referred to as a D2D terminal. In addition, in the following description, “UE” may refer to a D2D user equipment. When it is necessary to distinguish between a transmitting end and a receiving end, a D2D terminal that transmits or intends to transmit data to another D2D terminal using a radio resource assigned to a D2D link during D2D communication is called a transmitting D2D terminal, and data from a transmitting D2D terminal The terminal that receives or intends to receive the terminal will be referred to as a receiving D2D terminal. When there are a plurality of receiving D2D terminals to receive or intend to receive data from the transmitting D2D terminal, the plurality of receiving D2D terminals may be distinguished through a first to N prefix. Furthermore, for convenience of explanation, hereinafter, arbitrary nodes of the network end such as a base station, a D2D server, and an access / session management server for access control between D2D terminals or allocating radio resources to the D2D link will be referred to as 'networks'. Let's do it.

In order to transmit data to other D2D devices via D2D communication, the D2D device needs to check the existence of D2D devices located in the periphery where data can be transmitted and received, and for this, D2D peer discovery (D2D peer discovery). ). The D2D UE performs D2D discovery within a discovery interval, and all D2D UEs may share the discovery interval. The D2D UE may receive D2D discovery signals transmitted by other D2D UEs by monitoring logical channels of the discovery area within the discovery period. The D2D terminals receiving the transmission signal of another D2D terminal prepare a list of adjacent D2D terminals using the received signal. In addition, it broadcasts its own information (ie, identifier) within the search interval, and other D2D UEs can receive the broadcast D2D discovery signal to know that the D2D UE exists within a range capable of performing D2D communication. .

Information broadcasting for D2D discovery may be performed periodically. In addition, such broadcast timing may be predetermined by the protocol and known to the D2D terminals. In addition, the D2D UE may transmit / broadcast a signal during a portion of the discovery interval, and each D2D UE may monitor signals that are potentially transmitted by other D2D UEs in the remainder of the D2D discovery interval.

For example, the D2D discovery signal may be a beacon signal. In addition, the D2D search periods may include a plurality of symbols (eg, OFDM symbols). The D2D user equipment may select / at least one symbol within the D2D discovery period to transmit / broadcast the D2D discovery signal. In addition, the D2D user equipment may transmit a signal corresponding to one tone in a symbol selected by the D2D user equipment.

After the D2D UEs discover each other through the D2D discovery process, the D2D UEs may perform a connection establishment process. For example, in FIG. 1, the first device 102 and the second device 106 may be linked to each other through a connection process. Thereafter, the first device 102 can send traffic to the second device 106 using the D2D link 108. The second device 106 can also send traffic to the first device 102 using the D2D link 108.

11 shows a simplified D2D communication network.

In FIG. 11, D2D communication between UEs UE1 and UE2 supporting D2D communication is performed. In general, a user equipment (UE) means a user's terminal, but when a network equipment such as an evolved Node B (eNB) transmits and receives a signal according to a communication scheme between the UEs (UE 1 and UE2), the eNB It may also be regarded as a kind of terminal.

UE1 may operate to select a resource unit corresponding to a specific resource in a resource pool, which means a set of resources, and transmit a D2D signal using the resource unit. UE2, which is a reception terminal, may configure a resource pool through which UE1 can transmit a signal, and detect a signal of UE1 in the corresponding pool. For example, when UE1 is in the connection range of the base station, the resource pool may inform the base station. Also, for example, when UE1 is outside the connection range of the base station, another terminal may inform UE1 of the resource pool or UE1 may determine the resource pool based on the predetermined resource. In general, a resource pool is composed of a plurality of resource units, and each terminal may select one or a plurality of resource units and use it for transmitting its own D2D signal.

12 illustrates a configuration of a resource unit according to an example.

In FIG. 12, the vertical axis represents frequency resources and the horizontal axis represents time resources. In addition, the radio resource is divided into N _T pieces on the time axis to configure N _T subframes. In addition, the frequency resource is divided into N _F on one subframe, and one subframe may include N _T symbols. Thus, a total of N _F * N _T resource units may be configured as a resource pool.

Since the D2D transmission resource (unit # 0) allocated to unit number 0 is repeated every N _T subframes, in the embodiment of FIG. 12, the resource poll may be repeated every N _T subframes. As shown in FIG. 12, certain resource units may appear periodically and repeatedly. In addition, in order to obtain a diversity effect in a time dimension or a frequency dimension, an index of a physical resource unit to which one logical resource unit is mapped may be changed according to a predetermined pattern. For example, the logical resource unit may be hopped on the time and / or frequency axis according to a predetermined pattern on the actual physical resource unit. In FIG. 12, a resource pool may mean a set of resource units that can be used for transmitting a signal by a terminal to which a D2D signal is to be transmitted.

The above-described resource pool may be subdivided into several types. For example, resource pools may be classified according to content of D2D signals transmitted from each resource pool. For example, the contents of the D2D signal may be classified as described below, and a separate resource pool may be set for each.

Scheduling Assignment (SA): SA (or SA information) is a location of resources used for transmission of a subsequent D2D data channel and a modulation and coding method necessary for demodulation of other data channels (Modulation). and Coding Scheme (MCS) and / or MIMO (Multiple Input Multiple Output) transmission scheme. In addition, the SA information may include an identifier (User Equipment Identifier) of the target terminal to which each transmitting terminal to transmit data. The signal including SA information may be multiplexed with D2D data on the same resource unit and transmitted. In this case, the SA resource pool may mean a resource pool in which scheduling allocation is multiplexed with D2D data and transmitted. .

-D2D data channel: The D2D data channel may mean a pool of resources used by a transmitting terminal to transmit user data by using resources designated through scheduling allocation. If the scheduling allocation can be multiplexed and transmitted together with the D2D resource data on the same resource unit, only a D2D data channel having a form other than the scheduling allocation information may be transmitted in the resource pool for the D2D data channel. That is, on an individual resource unit in the SA resource pool, a resource element for transmitting scheduling allocation information may be used for transmitting D2D data on the resource pool of the D2D data channel.

Discovery message: The discovery message resource pool means a resource pool for transmitting a discovery message that allows a transmitting terminal to transmit information such as its identifier (ID) so that neighboring terminals can discover itself. can do.

As described above, the D2D resource pool may be classified according to the content of the D2D signal. However, even if the contents of the D2D signal are the same, different support pools may be used depending on the transmission / reception attributes of the D2D signal. For example, even when the same D2D data channel or discovery message is transmitted, the transmission timing determination method of the D2D signal (for example, is transmitted at the time of reception of a synchronization reference signal or is applied by applying a certain timing advance at the time of reception). Resource allocation scheme (e.g., whether the eNB assigns a transmission resource of an individual signal to an individual transmission terminal or whether an individual transmission terminal selects its own transmission resource of an individual signal within a resource pool), or a signal format ( For example, each D2D signal may be divided into different resource pools according to the number of symbols occupied by one subframe or the number of subframes used to transmit one D2D signal.

As described above, the UE that wants to transmit data using D2D communication may first select an appropriate resource from the SA resource pool and transmit its own scheduling allocation (SA) information. In addition, for example, as the selection criteria of the SA resource pool, it is expected that there will be no data transmission in a resource not used for transmission of SA information of another terminal and / or a subframe following transmission of SA information of another terminal. The SA resource associated with the resource may be selected as the SA resource pool. In addition, the UE may select an SA resource linked to a data resource that is expected to have a low interference level. In addition, SA information may be broadcasted. Accordingly, terminals in the D2D communication system may receive broadcasted SA information. In the following description, "send" or "send" may be replaced with "broadcasting".

13 illustrates a periodic SA resource pool according to an example.

For example, an SA resource pool may appear prior to a series of D2D data channel resource pools. The terminal may first attempt to detect the SA information, and when the existence of the data that the terminal needs to receive is found, may attempt to receive data from the data resource associated with the terminal. For example, the resource pool may be composed of a preceding SA resource pool and a subsequent data channel resource pool, as shown in FIG. 13. As shown in FIG. 13, an SA resource pool may appear periodically. In the following description, the period in which the SA resource pools appear may be referred to as an SA period.

As described above, in D2D communication, a signal may be transmitted using a conventional uplink resource. In the communication using the uplink resource, MIMO technology may be applied to obtain diversity by using multiple antennas.

Two types of MIMO techniques can be used to achieve diversity. First, a closed loop MIMO scheme in which feedback information on a channel is used may be used. In addition, an open loop MIMO scheme in which feedback information on a channel is not used may be used. In general, the closed loop MIMO scheme tends to have higher performance than the open loop MIMO scheme because it uses feedback information for channel conditions. However, if the feedback information on the channel state is not accurate, the open loop MIMO scheme may have higher performance than the closed loop MIMO scheme.

For example, in D2D communication, many devices may use multiple antennas to ensure diversity. In this case, if the closed loop MIMO scheme is applied, feedback information for each of the multiple antennas of each device should be exchanged between the transmitting side and the receiving side. Therefore, the amount of feedback information can be greatly increased. This increase in feedback information can reduce the amount of radio resources for data transmission and cause inefficiency. Thus, using an open loop MIMO scheme may be more efficient.

Also, for example, in D2D communication, the transmitting side or the receiving side may be a vehicle or a communication device provided in the vehicle. When the vehicle moves at high speed, the channel state between the transmitting side and the receiving side can change rapidly. If the channel state changes rapidly, feedback information on the channel state may be inaccurate. Thus, using an open loop MIMO scheme may be more efficient.

Embodiments of the present application proposed below may be applied not only to D2D communication using uplink resources but also to conventional communication using uplink resources.

In Embodiment 1, a method of applying precoding based on a DMRS port (Demodulation Reference Signal port) of an uplink resource, but changing the precoding on a time axis, is proposed.

14A and 14B illustrate a configuration diagram of radio resources for uplink MIMO according to an embodiment of the first embodiment.

14A shows the allocation of DMRS to a normal cyclic prefix (CP) and FIG. 14B shows the allocation of DMRS to an extended CP.

In the following description, D1 means a resource element (RE) transmitted by the first DMRS port, and D2 means a resource element (RE) transmitted by the second DMRS port. Further, the channel vector from the first DMRS port to the receive antenna is

The channel vector from the second DMRS port to the receive antenna is

May be called.

Also, different precodings for each OFDM symbol on the time axis

Can be applied.

Where s represents the OFDM symbol index. The transmitting end precodes the DMRS port for each OFDM symbol index in the remaining resource elements except for the resource element in which the DMRS is transmitted.

Apply, and transmit data to which precoding is applied. In this case, the received signal at the receiving end may be expressed by Equation 14 below.

[Equation 14]

In Equation 14,

Represents the data vector transmitted from the transmitter,

Denotes a thermal noise vector of the receiver. In Equation 14, precoding may be changed and applied for each OFDM symbol. Such

Is determined in advance between the transmitter and the receiver for each OFDM symbol, or the transmitter corresponds to each OFDM symbol at the receiver.

You can also tell. The receiving end estimates the channels of the first DMRS port and the second DMRS port using resource elements of the positions D1 and D2.

The received data can be detected using. In this way, diversity can be ensured at the receiving end by transmitting a signal by applying precoding in accordance with an OFDM symbol on the time axis.

In addition, precoding

May be a subset of the precoding of Table 3 used in the current uplink precoding. Table 3 shows precoding currently used for uplink.

TABLE 3

For example, if two layers are used,

With, additionally

Precoding may be applied. Two precodings can be applied alternately on the antenna port where each layer is transmitted on the time axis.

Also, for example, precoding

Is designed using

codebook indexes

4 and 5 of Table 3, the application of precoding for each symbol may operate in the same manner as the operation of port selection for each OFDM symbol. For example, as shown in FIG. 15A, except for the OFDM symbols of index 3 and index 10 in which DMRSs are transmitted, the

codebook indexes

4 and 5 of Table 3 may be alternately applied to each OFDM symbol in the remaining OFDM symbols. have. In the remaining OFDM symbols except for OFDM symbols for DMRS transmission for the extended CP, an embodiment in which codebook

indexes

4 and 5 of Table 3 are alternately applied to each OFDM symbol is illustrated in FIG. 15B. As shown in FIGS. 15A and 15B, the application of cross precoding for each OFDM symbol is the same as the operation of alternately selecting the first DMRS port and the second DMRS port.

In addition, in the port selection, the resource estimation around the resource element to which the DMRS is transmitted may perform channel estimation more accurately. Accordingly, OFDM symbols adjacent to OFDM symbols on which DMRSs are transmitted may be used by an antenna port of DMRS corresponding to adjacent OFDM symbols. For example, as illustrated in FIG. 16A, a first DMRS port may be used around the D1 DMRS (OFDM symbol index 3), and a second DMRS port may be used around the D2 DMRS (OFDM symbol index 10). When the present embodiment is applied to the extended CP, a radio resource may be allocated as shown in FIG. 16B.

On the other hand, in the first embodiment, precoding

May not have different values for every s. For example, precoding for some different s

May be the same.

In addition, precoding

May be defined according to several patterns. Precoding

Information about one of the predetermined patterns for the UE may be transmitted to the terminal through Radio Resource Control (RRC) signaling, Downlink Control Information (DCI), and / or Physical Sidelink Discovery Channel (PSCH). Also, the pattern may be determined according to the fixed value. For example, in D2D communication, the physical sidelink broadcast channel (PSBCH), the physical sidelink control channel (PSCCH), the physical sidelink discovery channel (PSCSCH), and the physical sidelink shared channel (PSSCH) are different from each other.

It may have a pattern of.

In Embodiment 1, since the D1 and the D2 use different DMRS ports, it may be difficult for the receiving end to estimate the frequency offset. When the first DMRS port and the second DMRS port transmit the same signal, the receiving end may estimate the frequency offset using the phase difference between D1 and D2. However, when D1 and D2 transmit different signals from each other, the receiving end must correct the frequency offset through the phase difference between D1 received in one subframe and D1 received in a subsequent subframe, Longer intervals can reduce accuracy.

Therefore, in the second embodiment, the DMRS may be transmitted on more OFDM symbols than the DMRS defined in the current LTE or LTE-A system. Also, for example, DMRS may be transmitted on two OFDM symbol indexes per one DMRS port in one subframe. In addition, the DMRS is precoded based on the DMRS port, and the precoding may be changed in the time axis.

For example, as shown in FIG. 17A (see FIG. 17B for an extended CP), a DMRS may be transmitted. In the following description, D1 means a resource element (RE) transmitted by the first DMRS port, and D2 means a resource element (RE) transmitted by the second DMRS port. Further, the channel vector from the first DMRS port to the receive antenna is

The channel vector from the second DMRS port to the receive antenna is

May be called.

Also, different precodings for each OFDM symbol on the time axis

Can be applied.

Apply, and transmit data to which precoding is applied. In this case, the reception signal at the receiving end that receives data from the first DMRS port and the second DMRS port may be expressed by Equation 14 above.

In Equation 14, precoding may be changed and applied for each OFDM symbol. Such

Is determined in advance between the transmitting end and the receiving end for each OFDM symbol, or the transmitting end for each OFDM symbol at the receiving end.

The received data can be detected using. As described above, by applying the precoding by changing the precoding according to the OFDM symbol on the time axis, diversity at the receiving end can be ensured.

Meanwhile, precoding

May be a subset of the precoding of Table 3 used in the current uplink precoding. Precoding using a subset of the six precodings listed in Table 3

May be generated. For example, if two layers are used,

With, additionally

Also, for example, precoding

Is designed using the

codebook indexes

4 and 5 of Table 3, the operation may be performed in the same manner as the port selection for each OFDM symbol. For example, as shown in FIG. 18A, except for the OFDM symbols of

indexes

2, 5, 8, and 11 in which DMRSs are transmitted, the

codebook indexes

4 and 5 of Table 3 are the same for each OFDM symbol in the remaining OFDM symbols. Can be applied alternately. 18B shows an embodiment in which codebook

indexes

4 and 5 of Table 3 are alternately applied to each OFDM symbol in the remaining OFDM symbols except for OFDM symbols for DMRS transmission for the extended CP. As shown in FIGS. 18A and 18B, the application of cross precoding for each OFDM symbol is the same as the operation of alternately selecting the first DMRS port and the second DMRS port.

In addition, in the port selection, the resource estimation around the resource element to which the DMRS is transmitted may perform channel estimation more accurately. Accordingly, OFDM symbols adjacent to OFDM symbols on which DMRSs are transmitted may be used by antenna ports of adjacent DMRSs. For example, as shown in FIG. 19A, a first DMRS port is used around D1 DMRS (OFDM symbol indexes 2 and 8), and a second DMRS port is used around D2 DMRS (OFDM symbol indexes 5 and 11). Can be. When the present embodiment is applied to the extended CP, a radio resource may be allocated as shown in FIG. 19B.

On the other hand, when using port selection as shown in Figs. 19A and 19B, for example, in D2D communication, D1 DMRS may be transmitted once more in the first OFDM symbol. For example, as shown in FIG. 20A, D1 DMRS may be transmitted in the first OFDM symbol. For example, D1 DMRS may be transmitted at

OFDM symbol indexes

0 and 8 for normal CP, and D2 DMRS may be transmitted at

OFDM symbol indexes

4 and 12 for normal CP. When the D1 DMRS is assigned to the first OFDM symbol, the receiver may try automatic gain control (AGC) for the first known OFDM symbol and use it for other OFDM symbols. Thus, efficient AGC can be performed.

Therefore, in consideration of the AGC, the arrangement of the DMRS as shown in FIG. 20A may be more preferable than the arrangement of the DMRS as shown in FIG. 17A. In addition, the remaining DMRSs may be arranged evenly apart on the time axis except for the DMRS disposed in the first OFDM symbol. Also, for example, an embodiment in which D1 DMRS is disposed in a first OFDM symbol for an extended CP is illustrated in FIG. 20B.

On the other hand, in the second embodiment, precoding

May be the same.

Embodiment 2 may have an advantage in the correction of the frequency offset because the frequency of the same DMRS port appears on the time axis compared to the first embodiment.

In addition, precoding

May be defined according to several patterns. Precoding

It may have a pattern of.

On the other hand, although there is an advantage in the correction of the frequency offset in the second embodiment, in the second embodiment, since more DMRS is transmitted than in the first embodiment, resource elements that can be used for data transmission are reduced. Accordingly, in order to prevent a decrease in the amount of transmitted data, subcarrier spacing may be doubled in an OFDM symbol in which the DMRS is transmitted, and the length of an OFDM symbol in which the DMRS is transmitted may be reduced by half.

For example, when the length of the DMRS of the embodiment of FIG. 20A is cut in half, the DMRS may be arranged as shown in FIG. 21A. As shown in FIG. 21A, an OFDM symbol to which a DMRS is transmitted has a length of half of an existing OFDM symbol and an OFDM symbol for other data transmission. In addition, the DMRS doubles the subcarrier spacing so that one DMRS is transmitted over two subcarriers. Therefore, while increasing the amount of DMRS, as shown in FIG. 21A, the second embodiment can be performed without reducing the amount of resource elements for data transmission. 21B shows an example in which the present embodiment is applied to an extended CP.

Meanwhile, as in Embodiment 1, DMRS is transmitted, but a plurality of DMRS ports may share one resource element. For example, within one subframe, all DMRS ports may share the same resource element. Each DMRS port may be identified using a cyclic shift or an orthogonal cover code (OCC). The value of the cyclic shift and / or orthogonal cover code may be sent to the receiving end using a scheduling assignment (eg, PSCCH). In addition, as described above in Embodiment 1, precoding may be applied based on a DMRS port, and precoding may be changed and applied on a time axis.

For example, the DMRS may be transmitted as shown in FIG. 22A. 22B shows an example where this embodiment is applied to an extended CP.

In the following description, D1 means a resource element (RE) transmitted by the first DMRS port, and D2 means a resource element (RE) transmitted by the second DMRS port. As shown in FIG. 22A, different DMRS ports share the same resource element. For example, DMRS ports may be separated using cyclic shift (CS) and / or orthogonal cover code (OCC) currently used for uplink DMRS of the LTE system. Further, the channel vector from the first DMRS port to the receive antenna is

The channel vector from the second DMRS port to the receive antenna is

May be called.

Also, different precodings for each OFDM symbol on the time axis

Can be applied.

Where s represents the OFDM symbol index. The transmitting end precodes the DMRS port for each OFDM symbol index in the remaining resource elements except for the resource element to be transmitted by DMRS.

In Equation 14, precoding may be changed and applied for each OFDM symbol. Such

Meanwhile, precoding

May be a subset of the precoding of Table 3 used in the current uplink precoding. Precoding using a subset consisting of the six precodings listed in Table 3

May be generated. For example, if two layers are used,

With, additionally

22A and 22B illustrate the case where two DMRS ports are used, but this is illustrative, and more DMRS ports may be used using cyclic shift (CS) and orthogonal cover code (OCC). Precoding when more DMRS ports are used

A permutation matrix can be used to determine. Or precoding

A selection matrix for selecting a DMRS port may be used to determine.

Also, for example, precoding

Is designed using the

codebook indexes

4 and 5 of Table 3, the operation may be performed in the same manner as the port selection for each OFDM symbol. For example, as shown in FIG. 22A, except for the OFDM symbols of

indexes

3 and 10 in which DMRSs are transmitted, the

codebook indexes

4 and 5 of Table 3 may be alternately applied to each OFDM symbol in the remaining OFDM symbols. . 22B shows an embodiment in which codebook

indexes

4 and 5 of Table 3 are alternately applied to each OFDM symbol in the remaining OFDM symbols except for OFDM symbols for DMRS transmission for the extended CP. As shown in Figs. 22A and 22B, cross precoding application per OFDM symbol is equivalent to alternately selecting the first DMRS port and the second DMRS port.

On the other hand, in the third embodiment, precoding

May be the same.

In addition, precoding

May be defined according to several patterns. Precoding

It may have a pattern of.

Meanwhile, according to Embodiment 2, resource elements for DMRS transmission in a subframe are increased, but resource elements having different OFDM symbol indices may be used for transmission of reference signals of different DMRS ports. In this embodiment, precoding is applied based on the DMRS port, and precoding may be changed and applied on the time axis.

For example, the DMRS may be transmitted as shown in FIG. 23A (see FIG. 23B for the extended CP). Here, D1 represents a resource element used by the first DMRS port, D2 represents a resource element used by the second DMRS port, D3 represents a resource element used by the third DMRS port, and D4 represents a first element. 4 Indicates resource element used by DMRS port. Further, the channel vector from the first DMRS port to the receive antenna is

The channel vector from the second DMRS port to the receive antenna is

The channel vector from the third DMRS port to the receive antenna

Thus, the channel vector from the fourth DMRS port to the receive antenna is

May be called.

Also, different precodings for each OFDM symbol on the time axis

Can be applied.

Apply, and transmit data to which precoding is applied. In this case, the received signal at the receiver may be expressed by Equation 15 below.

[Equation 15]

In Equation 15,

Represents the data vector transmitted from the transmitter,

Denotes a thermal noise vector of the receiver. In Equation 15, precoding may be changed and applied for each OFDM symbol. Such

You can also tell. The receiving end estimates a channel of the first DMRS port, the second DMRS port, the third DMRS port, and the fourth DMRS port by using resource elements at positions D1, D2, D3, and D4.

In the example of embodiment 4, an example is described in which four DMRS ports are used. However, the present embodiment is not limited thereto and may be applied to any other number of DMRS ports. In Example 4, precoding

A permutation matrix can be used to determine. In addition, precoding

A selection matrix for selecting a DMRS port may be used to determine.

For example, precoding

Is a selection matrix

,

, And

It may be designed using. This may be performed in the same manner as the port selection for each OFDM symbol. For example, as shown in FIG. 23A, the selection matrix is for the remaining OFDM symbols except for the

OFDM symbol indexes

2, 5, 8, and 11 used for transmission of the DMRS.

,

, And

It can be applied alternately as this precoding. That is, sequential application of the selection matrix is the same as the operation of sequentially selecting

DMRS ports

1, 2, 3, and 4 for each OFDM symbol.

In addition, in port selection, more accurate channel estimation may be performed on resource elements around the DMRS port. Therefore, OFDM symbols adjacent to the OFDM symbol to which the DMRS is transmitted may be used by the DMRS port of the adjacent DMRS.

In addition, precoding

May be a subset of the precoding of Table 3 used in the current uplink precoding.

On the other hand, in D2D communication, DMRS is transmitted on the first OFDM symbol of a subframe for improved automatic gain control (AGC), and the remaining DMRSs may be arranged to fall evenly on the time axis.

On the other hand, in the fourth embodiment, precoding

May be the same.

In addition, precoding

May be defined according to several patterns. Precoding

It may have a pattern of.

In FIGS. 23A and 23B, resource elements that can be used for data transmission may be reduced due to an increase in DMRS in a subframe. Thus, in order to prevent the reduction of resource elements for data transmission, the length of the symbol on which the DMRS is transmitted is reduced in half, and the subcarrier spacing of the DMRS may be doubled.

As shown in FIG. 24A (for an extended CP, see FIG. 24B), the OFDM symbols (

OFDM symbol indexes

2, 6, 9, and 13) in which the DMRSs of each DMRS port are transmitted are half the length of the remaining OFDM symbols. Has In addition, each DMRS has twice the subcarrier spacing than the conventional DMRS. Thus, each DMRS is transmitted over two subcarriers. Accordingly, by arranging the DMRS as shown in FIGS. 24A and 24B, the DMRS transmission according to the fourth embodiment can be performed while preventing the reduction of resource elements for data transmission.

Example 5

In

Embodiments

1, 2, 3, and 4 described above, precoding is changed and applied on the time axis for OFDM symbols. In addition, in Embodiment 5, the precoding may be changed and applied not only in the time axis but also in the frequency axis.

In Embodiment 5, on one OFDM symbol index, several DMRS ports are transmitted separately on the frequency axis. That is, when N DMRS ports are transmitted on one OFDM symbol, each DMRS port transmits a reference signal (e.g., DMRS) for every N resource elements on the frequency axis so that reference signals do not overlap each other. Can be configured. In addition, in this embodiment, precoding is applied based on the DMRS port, and precoding may be changed and applied on the time axis and the frequency axis.

For example, as shown in FIG. 25A (for an extended CP, see FIG. 25B), DMRSs from two DMRS ports may be transmitted.

The channel vector from the second DMRS port to the receive antenna is

May be called.

Also, different precodings for each resource element

Can be applied.

Where s represents an OFDM symbol index and f represents a frequency unit. In current LTE and LTE-A communication systems, one resource element can be designated by designating time and frequency as shown in (s, f). The transmitting end precodes the DMRS port for each resource element, except for the resource element to which DMRS is transmitted.

Apply, and transmit data to which precoding is applied. In this case, to stabilize the peak-to-average power ratio (PAPR),

May apply. Under the above conditions,

Is a period on the frequency axis

Each has the same value. Therefore, when the above conditions are satisfied, since the signal is transmitted in the form of Interleaved Frequency-Division Multiple-Access (IFDMA), PAPR can be stabilized. The received signal at the receiver may be expressed by Equation 16 below.

[Equation 16]

In Equation 16 above,

Represents the data vector transmitted from the transmitter,

Denotes a thermal noise vector of the receiver. In Equation 16, precoding may be changed and applied for each OFDM symbol and for each subcarrier. Such

Is predetermined between the transmitting end and the receiving end for each OFDM symbol and / or for each subcarrier,

The received data can be detected using. In this way, by applying the precoding by changing the OFDM symbol on the time axis, the diversity at the receiving end can be ensured.

25A and 25B illustrate the case where two DMRS ports are used, but this is exemplary and more DMRS ports may be used using cyclic shift (CS) and orthogonal cover code (OCC). Precoding when more DMRS ports are used

A permutation matrix can be used to determine. Or precoding

A selection matrix for selecting a DMRS port may be used to determine.

In the example of FIGS. 25A and 25B, two DMRS ports are used, but the fifth embodiment is not limited thereto, and a plurality of DMRS ports may be used. For example, if four DMRS ports are used, the DMRS may be transmitted as shown in FIGS. 26A-28B.

First, an example in which the embodiment of FIGS. 25A and 25B described above is applied to four DMRS ports is shown in FIGS. 26A and 26B (for an extended CP).

In FIG. 27A, similar to Embodiment 2 described above, the OFDM symbol for DMRS transmission is increased. With regard to FIG. 27A, the descriptions above with respect to Embodiment 2 and Embodiment 5 are omitted to avoid duplicate description. Meanwhile, in the case of the extended CP, the DMRS may be transmitted as shown in FIG. 27B.

In FIG. 28A, a modified embodiment of FIG. 27A is shown. In FIG. 28A, instead of all DMRS ports being repeated on one OFDM symbol, only some groups of DMRS ports are repeated on one OFDM symbol. For example, DMRS (D1) of the first DMRS port and DMRS (D2) of the second DMRS port are repeated on

OFDM symbol indexes

2 and 8, and DMRS (D3) of the third DMRS port on

OFDM symbol indexes

5 and 11. And DMRS (D4) of the fourth DMRS port may be repeated. Meanwhile, in the case of the extended CP, the DMRS may be transmitted as shown in FIG. 28B.

In Example 5,

The substitution matrix can be used to determine. Also,

May be determined based on a selection matrix for selection of a DMRS port.

As described above, in D2D communication, in consideration of automatic gain control, a DMRS is allocated to the first OFDM symbol, and the remaining DMRSs may be evenly spaced apart on the time axis. A specific arrangement method of DMRSs in consideration of automatic gain control may be referred to the first to fourth embodiments.

In addition, in Example 5,

May not necessarily have different values for each resource element. For example, any different resource elements may be the same

May have a value.

In addition, precoding

May be defined according to several patterns. Precoding

It may have a pattern of.

On the other hand, when the DMRS is transmitted according to the embodiment of Figs. 27A to 28B, since the time interval between the DMRS of the same DMRS port is shortened, the frequency offset can be more efficiently performed. However, in order to prevent the decrease of the OFDM symbol for data transmission due to the increase of the DMRS, the subcarrier spacing in the symbol in which the DMRS is transmitted may be doubled, and the length of the symbol may be reduced by half. have. Detailed information related to this may be referred to by the above-described description in Embodiments 2 to 4 above.

On the other hand, in the above-described embodiments 1 to 5, the term DMRS port may mean to refer to the antenna port corresponding to the DMRS.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

It is apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit and essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

The MIMO technology support method for the uplink as described above and an apparatus therefor have been described with reference to the example applied to the 3GPP LTE system, but it can be applied to various wireless communication systems in addition to the 3GPP LTE system.

Claims

A signal transmission method of a terminal on a wireless communication system supporting multiple antennas,

First demodulation reference signals (DMRSs) corresponding to the first antenna port and second DMRSs corresponding to the second antenna port in the first Orthogonal Frequency Division Multiplexing (OFDM) symbols in the subframe; Mapping;

Mapping first data corresponding to the first antenna port and second data corresponding to the second antenna port to second OFDM symbols except for the first OFDM symbols in the subframe; And

Transmitting the subframe using resources allocated to uplink,

Predetermined precodings are applied to the first data and the second data,

The predetermined precodings are changed according to the index of the second OFDM symbols.
The method of claim 1,

And the first data and the second data are alternately mapped on the second OFDM symbols.
The method of claim 1,

The first data is mapped to be adjacent to an OFDM symbol to which the first DMRSs are mapped among the first OFDM symbols,

And the second data is mapped such that the second DMRSs of the first OFDM symbols are adjacent to the mapped OFDM symbol.
The method of claim 1,

And the predetermined precodings are determined as one of the predetermined precoding patterns.
The method of claim 4, wherein

And transmitting information corresponding to the preset precoding to a receiving end.
The method of claim 1,

The first OFDM symbols include four OFDM symbols,

Wherein the first DMRSs are mapped onto two OFDM symbols of the first OFDM symbols, and the second DMRSs are mapped onto the remaining two OFDM symbols of the first OFDM symbols.
The method of claim 6,

One of the first OFDM symbols is mapped to the first OFDM symbol of the subframe, and the remainder of the first OFDM symbols are mapped to each other at equal intervals on the time axis.
The method of claim 6,

The first OFDM symbols have a length of half the length of the second OFDM symbol on the time axis,

Wherein each of the first DMRSs and each of the second DMRSs are mapped across two subcarriers.
The method of claim 1,

The first OFDM symbols include two OFDM symbols,

The first DMRS and the second DMRS share the first OFDM symbols with resource elements, respectively.

Wherein the first DMRS and the second DMRS are separated using a cyclic shift and an orthogonal cover code.
The method of claim 1,

The predetermined precodings are changed according to an index of the second OFDM symbols and a subcarrier of the subframe.
The method of claim 10,

The predetermined precodings are configured to have the same value every predetermined frequency period.
The method of claim 10,

And the first DMRS and the second DMRS are alternately mapped on resource elements of each of the first OFDM symbols.
A signal receiving method of a terminal on a wireless communication system supporting multiple antennas,

Receiving a subframe from a first antenna and a second antenna of a transmitting end by using a resource allocated to an uplink; And

Estimating a channel from the first antenna and a channel from the second antenna based on predetermined precodings applied to the first data from the first antenna and the second data from the second antenna. Including steps

First demodulation reference signals (DMRSs) corresponding to the first antenna port and second DMRSs corresponding to the second antenna port are included in first orthogonal frequency division multiplexing (OFDM) symbols in the subframe. Mapped,

First data corresponding to the first antenna port and second data corresponding to the second antenna port are mapped to second OFDM symbols except for the first OFDM symbols in the subframe,

The predetermined precodings are changed according to the index of the second OFDM symbols.
A terminal on a wireless communication system supporting multiple antennas,

A transmitter for transmitting a signal; And

A processor configured to control the transmitter,

The processor,

First demodulation reference signals (DMRSs) corresponding to the first antenna port and second DMRSs corresponding to the second antenna port in the first Orthogonal Frequency Division Multiplexing (OFDM) symbols in the subframe; Mapping,

Mapping first data corresponding to the first antenna port and second data corresponding to the second antenna port to second OFDM symbols excluding the first OFDM symbols in the subframe,

Further configured to transmit the subframe using resources allocated for uplink,

Predetermined precodings are applied to the first data and the second data,

The preset precodings are changed according to the indexes of the second OFDM symbols.
A terminal on a wireless communication system supporting multiple antennas,

A receiver for receiving a signal; And

A processor configured to control the receiver,

The processor,

Receiving a subframe from the first antenna and the second antenna of the transmitting end by using the resources allocated to uplink,

Estimate a channel from the first antenna and a channel from the second antenna based on predetermined precodings applied to the first data from the first antenna and the second data from the second antenna. More organized,

First demodulation reference signals (DMRSs) corresponding to the first antenna port and second DMRSs corresponding to the second antenna port are included in first orthogonal frequency division multiplexing (OFDM) symbols in the subframe. Mapped,

First data corresponding to the first antenna port and second data corresponding to the second antenna port are mapped to second OFDM symbols except for the first OFDM symbols in the subframe,

The preset precodings are changed according to the indexes of the second OFDM symbols.